Greek vampires that would feed on children born around Christmas time.
Nativity (Holy Night, Christmas) - Lucas Cranach the Elder
A type of Greek vampire called “callicantzaros” was unique in that it could only go about its activities on Christmas Day and the week or 12 days afterwards. Children born during the week between Christmas and New Years, or Christmas and the Epiphany (when the three wise men are said to have arrived at Bethlehem to present their gifts) were described as ‘feast-blasted’ and believed to be predestined to become vampires. These vampires would roam the netherworld and emerge on Christmas Day to seize people with its extended fingernails and tear them to pieces. Unfortunately, this belief led people to look with fear and hostility upon anyone born during the forbidden period.